It is known that health-promoting effects are attributed to glucans from fungi and yeasts. “Shiitake” fungus (Lentinus edodes) has been attributed effects which can be exploited for many medicinal purposes such as immunestimulation, anti-virus, anti-tumor, etc. Studies of lentinan have shown that it stimulates the immune system of the host in a variety of ways, such as activation of T helper cells, increased production of Interleukin 1 and Interleukin 2, increased antibody production in various forms of cancer, and decreasing the cholesterol level in the blood. (Herbs for Health, January/February, 1997; K. Jones, “Shiitake: Medicine in a mushroom”, p. 40-50, 54; Anticancer Res, Vol. 17(4A), 1997; H. Matsouka, “Lentinan potentiates immunity and prolongs the survival time of some patients”, p. 2751-2755; Adv Appl Microbiol, Vol. 39, 1993; S. C. Jong, “Medicinal and therapeutic value of the shiitake mushroom”, p. 153-184, Int J Immunopharmacol, Vol. 14, 1992; K. Irinoda, “Stimulation of microbiocidal host defense mechanism against aerosol influenza virus infection by lentinan, p. 971-977, Jpn J Cancer Res, Vol. 76(1), 1985; D. Herlyn, “Monoclonal antibody-dependent murine macrophage-mediated cytotoxicity against human tumors is stimulated by lentinan, p. 37-42).
One active ingredient of Lentinus edodes is termed lentinan, a polysaccharide based compound described as a beta-(1,3) glucan backbone with beta-(1,6) side chains.
“Solid-state” reactors are routinely used for culturing fungi such as Lentinus edodes. This is a technology which is used for many purposes such as composting, production of biological products such as enzymes, soy sauce, acetic acid, and the like. For the production of lentinan, Lentinus edodes can be cultivated on a suitable solid matrix provided by stems of tree or chips of wood to which is often added chemical compounds supporting the growth of mycelium and development of the fruiting bodies, where most of the lentinan is localised. The fruiting bodies are harvested, either by hand or mechanically, and are subsequently dried and ground to a powder which can be used as it is, or used in tablets, or sent for further processing such as extraction of lentinan.
A polysaccharide product prepared from Lentinus edode is commercially available as “Lentinan for injection” (Eureka Bio-Chemicals Pty, Australia). This product has some immunestimulating effect (see also the examples herein below).
The patent application WO03/020944 describes a number of methods of purifying extracellular immunestimulating compounds from fungi. In general these methods involve a precipitation step.
However, compositions with very high immunestimulating activity have not been disclosed. It is therefore an object of the present invention to provide novel compositions, preferably extracellular immune stimulating agents from fungi with high level of immune modulating activity.